1. Field of the Invention
The present invention relates to a snow vehicle with a four-cycle engine installed thereon.
2. Description of the Related Art
Conventionally, two-cycle engines have been dominant as engines installed on snow vehicles, because of their relatively simple construction, lightweight, compact size, and high output power. However, more and more four-cycle engines have come to be used for snow vehicles due to the restrictions on exhaust emissions and demand for improved fuel economy in recent years. The four-cycle engines are more complicated in construction than the two-cycle engines, and therefore require a large installation space within the engine room. Further, in a vehicle where a supercharger (turbocharger) and an intercooler as an auxiliary associated therewith are installed, the installation space within the engine room becomes more limited, and the overall height of the engine tends to be increased.
In a snow vehicle in general, an engine room is defined inside an engine hood in front of a handle bar, and an engine is accommodated in the engine room. Further, a headlight is disposed in the vicinity of the handle bar. For this arrangement, the engine hood is shaped e.g. such that it slopes down toward the front from its highest point immediately below the headlight. Therefore, to save space, various component parts need to be efficiently laid out in the limited space within the engine room.
To suppress the overall height of the engine, it has been proposed to dispose a supercharger in front of the engine e.g. by Japanese Laid-Open Patent Publication (Kokai) No. 2001-214750(first prior art snow vehicle).
When the supercharger is installed to suppress the overall height of the engine, as in the case of the first prior art snow vehicle, the engine room is so crowded with components parts that cooling air does not flow smoothly within the engine room. Further, when the supercharger is disposed in front of the engine, there is a fear of intense heat from the supercharger affecting component parts disposed rearwardly of the supercharger.
For vehicles without a supercharger installed thereon, there has also been proposed, e.g. by Japanese Laid-Open Patent Publication (Kokai) No. H08-91277 (second prior art snow vehicle), a technique of enhancing cooling efficiency by separating a muffler section and the cooling system of an engine from each other using a partition that separates between a muffler room and an engine room.
When a supercharger and an intercooler are installed, however, while the supercharger generates intense heat, the intercooler needs to have high cooling efficiency. What is more, a clutch mechanism, a muffler, and so forth are also heat sources, and hence, how to form streams of cooling air is an important factor to be considered in designing the layout of the interior of the engine room, to ensure sufficient cooling efficiency of the intercooler.
Further, it is also necessary to consider the locations of component parts, such as a battery, which should not be exposed to intense heat. Furthermore, the number of component parts that generate heat within the engine room tends to increase, as can be understood from the example of installation of the turbocharger. Therefore, there is room for considering the way to make effective use of warm air which has been heated when passing through the engine room.